Spinal implant revision device

ABSTRACT

A spinal implant revision device has a revision connector and a tulip member. The revision connector is configured for attachment to a pre-existing rod in a patient. The revision connector has a slotted opening configured to receive a first or a pre-existing rod. The tulip member is pivotally connected to the revision connector and movable in angularity within predetermined ranges in a first plane. This first plane is parallel to a rod to which the revision connector is attached. A second plane which is non-parallel to that first plane allows a second or new rod to be received in the tulip and allows the second rod to pivot relative to the first rod.

TECHNICAL FIELD

This invention relates to a surgical instrument useful in bone fixationprocedures and methods of use thereof; and more particularly to a systemand devices for percutaneously revising existing pedicle screwassemblies for adding additional levels without removal of thepre-existing implants.

BACKGROUND OF THE INVENTION

There are many different approaches taken to alleviate or minimizesevere spinal disorders. One surgical procedure commonly used is aspinal fusion technique. Spinal fusion is a standard back surgicaltechnique and its use continues to rise. In addition to the spinalimplants or use of bone grafts, spinal fusion surgery often utilizesspinal instrumentation or surgical hardware, such as pedicle screws,plates, or spinal rods. Once the spinal spacers and/or bone grafts havebeen inserted, a surgeon places the pedicle screws into a portion of thespinal vertebrae and attaches either rods or plates to the screws as ameans for stabilization while the bones fuse.

While spinal fixation procedures can have positive outcomes, adjacentsegment degeneration (ASD) often follows fusion surgeries. In additionto requiring the fusion of additional spinal segments, patientssuffering from ASD often require posterior pedicle screw rod fixation.Such cases can be difficult for the surgeon as the surgical procedureoften requires “opening” of the patient's back to expose the entiresystem in order for the surgeon to get to the top tulip. Such procedureis not beneficial to the patient as it exposes them to increased pain,higher morbidity, worsening of paraspinal muscle fibrosis/atrophy.Should the surgeon need to completely remove the old system, trying toremove an existing rod in order to provide a new construct can betechnically difficult. Moreover, given the number of different spinalfixation systems in the market, knowing what system the patient containsand having the right tools to work on that system is a challenge.

There exists, therefore, a need for an improved devices and systems forextending a patient's existing fixation hardware which does not requireopen dissection, reduces the disruption of post tension bands, and canbe used with any existing pedicle screw system in place.

SUMMARY OF THE INVENTION

A spinal implant revision device has a revision connector and a tulipmember. The revision connector is configured for attachment to apre-existing rod in a patient. The revision connector has a slottedopening configured to receive a first or a pre-existing rod. The tulipmember is pivotally connected to the revision connector and movable inangularity within predetermined ranges in a first plane. This firstplane is parallel to a rod to which the revision connector is attached.A second plane which is non-parallel to that first plane allows a secondor new rod to be received in the tulip and allows the second rod topivot relative to the first rod.

The spinal implant revision has the second plane lying transverse to thefirst rod and allows the second rod inside the tulip to move within apredetermined angle range θ to θ+ on assembly relative to the first orpre-existing rod. The angular movement is achieved by a two piecesaddle. The angular range within the second plane is θ− to θ+ between−15 degrees and 15 degrees wherein 0 degrees is perpendicular to thefirst or pre-existing rod, the range of angles θ− to θ+ allows the newrod to be angled relative to the first or pre-existing rod inward oroutward relative to the first or pre-existing rod to permit installationdirectionally within the second plane toward or away from a centerlineof a spine. The spinal implant revision device allows the tulip torotate within the first plane a predetermined angular range α− to α+.This rotation and angular range is limited by a truncated “V” shapedslot or recess in the revision connector and a protrusion on the tulip.The angular range of α− to α+ is between −15 degrees to 15 degreeswherein 0 degrees is parallel to a longitudinal axis of the pre-existingrod, the range of angles α− to α+ allows the second or new rod to betilted either upwardly or downwardly relative to the first orpre-existing rod to permit installation at different levels relative tothe spine.

The spinal implant revision wherein the tulip member has a lower rodreceiving portion and an elongated tower portion connected integral tothe lower rod receiving portion by a breakaway groove positionedtherebetween. The lower rod receiving portion has a receiving slot orchannel extending to a closed end, a pair of legs extend from the closedend defining the channel past a pair of breakaway grooves. A pair ofdetachable leg extensions has one leg extension extending from each ofthe breakaway grooves and aligned with a leg further extending thechannel toward a proximal end. The leg extensions and the legs haveinternal threads to receive a compression screw for securing the secondor new rod. At or near the proximal end of the leg extensions furtherhas a pair of bridge connections spanning the respective channelconnecting each leg extension.

The slotted opening or channel extends through and between legs and legextension to receive a second or new rod therethrough external of apatient and configured to deliver said rod internal an incision to theclosed end of the tulip inside the patient. The tulip has a projectionconfigured to limit the angle of angular movement α− to α+ within atruncated “V” slot or recess on the revision connector. The projectionextending between the tulip and the first connector member, the firstconnector member further comprises a slot to receive the projection andsized larger to permit the range of angularity α− to α+. The revisionconnector has a shaft extending outwardly for coupling to the tulip. Thetulip has a first receiving hole for passing a shaft and a secondreceiving hole for engaging an end of the shaft. The end of the shafthas a chamfered cavity to receive a swedging tool to enlarge and flattenthe end of the shaft to secure the connector and tulip as an assembly.

The revision connector has the slotted opening for receiving a first orpre-existing rod extends inwardly toward the tulip to a closed end. Thefirst connector member has a threaded opening above the slotted openingto receive a threaded set screw with a convex or conical orfrustoconical shaped tip, and wherein tightening the set screw directsthe tip of the set screw to engage the first or pre-existing rodexternal surface outward of the rod's longitudinal axis as tightening ofthe set screw draws the first connector member closed end to movetightly against the first or pre-existing rod securing the first orpre-existing rod between the closed end and the tip of the set screw.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described by way of example and with reference tothe accompanying drawings in which:

FIG. 1 is a perspective view of the spinal implant revision device withexemplary first or pre-existing rod and a second or new rod attached.

FIG. 2 is a cross-sectional perspective view of the spinal implantrevision device from FIG. 1.

FIG. 3 is an exploded perspective view of the spinal implant revisiondevice of FIG. 1.

FIG. 4 is a plan end view of the spinal implant revision device of FIG.1.

FIG. 5 is a plan top view of the spinal implant revision device of FIG.1.

FIG. 6 is a plan front side view of the spinal implant revision deviceof FIG. 1.

FIG. 7 is a plan bottom view of the spinal implant revision device ofFIG. 1.

FIGS. 7A, 7B and 7C are views of the revision connector with β angles of0, 10 and 20 degrees inclination of the shaft relative to the recessedslot.

FIG. 8 is a plan rear end view of the spinal implant revision device ofFIG. 1.

FIG. 9 is a plan rear side view of the spinal implant revision device ofFIG. 1.

FIG. 9A is a cross-section view taken along lines A-A of FIG. 9.

FIG. 9B is an enlarged cross-section view taken from FIG. 9A.

FIG. 9C is a partial view showing the connector truncated “V” slot tolimit the angular range α− to α+.

FIG. 9D is an enlarged view of a portion of the revision connector takenfrom FIG. 9C.

FIG. 10 illustrates a final assembly of the spinal implant device shownattached to a first or pre-existing rod construct shown in a topperspective view.

FIG. 11 is a top perspective view of the final assembly as shown in FIG.10 demonstrating an angularity α within the range of α− to α+.

FIG. 12 is a side perspective view of the final assembly of FIG. 10showing the angularity θ within the range of θ− to θ+.

DETAILED DESCRIPTION OF THE INVENTION

With reference to FIGS. 1-9, the spinal implant revision device 10 ofthe present invention is illustrated. In addition, with reference toFIGS. 10-12, this spinal implant revision device 10 is shown connectedto a spinal column where a pre-existing spinal rod assembly 200 is shownwith the revision connector 12 physically attached to the pre-existingrod 101.

With reference to FIG. 1, the spinal implant revision device 10 isillustrated shown attached to a first rod 101, the first rod 101 can bea pre-existing rod already implanted into a patient's spinal column. Thesecond rod 102, as illustrated, can be a new rod for fixation ofadjacent vertebrae. As shown, the first rod 101 is attached to arevision connector 12, hereinafter referred to as connector 12. Theconnector 12 has a slotted opening or end 15 which receives thepre-existing rod 101. As shown, the slotted opening or end 15 fits undera top portion of the connector 12 and extends to closed end of theslotted opening 15. The lower portion of the connector 12 is shownsomewhat truncated and shorter than the upper portion. This enables theconnector 12 to fit easily downward and over a pre-existing rod 101.Once assembled, a set screw 40 is shown that threads into threads 14 andaffixes the rod 101 to the connector 12.

As further shown in FIGS. 1-3, with regard to the second rod 102 and itsassembly to the implant device 10 is shown a tulip 22. The tulip 22 hasa slotted configuration having legs 22A, 22B that project upwardly froma closed end of the tulip 22. These legs 22A, 22B have internal threads21 as illustrated. As shown, there is a breakaway feature 29 that is cutinto and partially through an external surface of the tulip 22. Abovelegs 22A, 22B of the tulip 22 is shown leg extensions 26, 28. These legextensions 26, 28 extend upward from the breakaway grooves 29 on eachside of the leg extensions 26, 28. As shown, these breakaway grooves 29can be cut into the tulip 22 in any number of ways. One preferred way isto form the breakaway portion of the groove 29 as described in U.S. Pat.No. 8,858,605 B1 issued Oct. 14, 2014 which is incorporated herein byreference in its entirety.

As mentioned, the leg extensions 26, 28 extend upwardly from thebreakaway grooves 29. During fabrication, it must be noted the legextensions 26, 28 are actually weldments that are welded to a portion ofthe lower portion of the tulip 22 prior to the breakaway groove 29 beingformed. This weldment line is shown as 23 in FIG. 1. This line 23 ispolished in such a fashion that the leg extensions 26, 28 form acontinuous cylindrical surface identical to the lower surface of thelegs 22A, 22B. Internal of the slotted end is a channel 24 which allowsa rod to be inserted in the channel 24. As shown the channel 24 iscompletely open on both sides of the leg extensions 26, 28 and the legs22A, 22B between the lower end of the channel 24 and outer bridges 27connecting the leg extensions 26, 28. At a lower portion of the tulip 22internal threads 21 are provided to receive a set screw. As shown, thesethreads 21 start in the leg extensions 26, 28 above the breakawaygrooves 29 into the lower legs 22A, 22B.

With reference to FIGS. 2 and 3, and more particularly to FIG. 3, anexploded view of the set screw 30 is shown. The set screw 30 hasexternal threads 32 that are complimentary to the internal threads 21 ofthe tulip 22. Inside the tulip 22 is an upper saddle portion 34 forfixing a rod 102 nested in a lower saddle portion 36. The upper saddleportion 34 and lower saddle portion 36 are configured to receive asecond rod 102 when fully inserted. As shown, the lower saddle portion36 is configured to fit directly over a shaft 16 of the connector 12.The shaft 16 of the rod connector 12 has a grooved end and is adapted tofit through receiving holes 113A, 113B in the lower portion of the tulip22. When this shaft 16 is projected inwardly into the tulip 22, the end17 can be compression staked in such a way that the end 17 flares outand secures the connector 12 to the tulip 22. When this is done, theassembly of these two parts is complete. As shown, on the side of thetulip 22 interposed between the connector 12 and the inner surface ofthe tulip 22 is a projection 114. This projection 114 fits into acomplimentary truncated “V” shaped recessed slot 109 on the connector 12and as such directionally limits the amount of angularity that can beachieved between the two parts, connector 12 and tulip 22. When theassembly is completed, as shown in FIG. 2, an externally threaded setscrew 40 with a convex tip 42 that can be conical or frustoconical orhemispherical is positioned on an external surface of the first rod 101outward of the longitudinal axis of the rod 101 in such a fashion thatas the set screw 40 is threaded into threads 14 and is tightened fully,it pulls the connector 12 against the rod 101 in a very tight and securefashion. When this occurs, the rod 101 and connector 12 are fixed toeach other.

As further shown, when the upper saddle portion 34 is positioned belowthe rod 102 in the tulip 22 a set screw 30 can be driven down over therod 102 in such a fashion that it secures the top of the rod 102 againstand inside a “U” slot in the upper saddle portion 34 along the rodsbottom “U” shaped surface of the lower saddle portion 36 and tightensagainst the shaft 16. This subsequently locks the rod 102 securely intothe tulip 22. When both rods 101, 102 are tightened and securedfastened, the tulip 22 cannot move relative to the connector 12. This issimilarly shown in FIG. 4.

With reference to FIG. 5, a top view of the assembly 10 is shown whereinthe recessed slot 109 and projection 114 are illustrated showing thatthe rods 101, 102 can move within a predetermined limited range α− to α+directionally such that an angularity can be created such that the tworods 101, 102 are not necessarily parallel, but can be tilted relativeto the other on inclinations. Further, with reference to FIG. 6,rotation of the tulip 22 can occur relative to the connector 12 withinthe limited range of α− to α+. This allows for a bending of the firstrod 101 relative to the second rod 102 such that at the tulip 22 andconnector 12 location, the rods 101, 102 can be bent such that anangularity is created such that one can be higher or lower relative tothe other and can be tilted relative to an angle α. These angles θ and αbecome fixed when the assembly is fully tightened.

In FIG. 7, the rod 102 when loosely fitted in the upper saddle portion34 can move angularly by an amount θ. The range of movement is limitedby the width of the channel 24 and the amount of movement, the uppersaddle portion 34 can make relative to the lower saddle portion 36 whichis fixed onto the shaft 16 of the connector 12. Whatever angle θ isachieved between this range of θ− and θ+ is set and fixed when the setscrew 30 is fully tightened inside the tulip 22.

FIG. 8 shows this construct, and with reference to FIG. 8, the set screw40 has the tip 42 pushing the rod 101 tightly against the slottedopening 15 of the connector 12.

FIGS. 9, 9A and 9B further illustrate this assembly in its finalconfiguration with all set screws 30, 40 fully engaged with theirrespective rods 102, 101. As shown, the shaft 16 of the connector 12 hasa depression 18 which is best illustrated in FIG. 3 and is also shown inFIG. 9B. Into this depression 18 sits the lower saddle portion 36 andupper saddle portion 34 fully illustrated in FIG. 9B. With reference toFIG. 9C, the revision connector 12 is shown separated from the tulip 22and tower 20 wherein the truncated “V” shaped recessed slot 109 and theprojection 114 are clearly visible. FIG. 9D is an enlarged view of therevision connector 12 showing the range of angles −α to +α that can beachieved within the truncated “V” shaped recessed slot 109. When thetulip 22 and the revision connector 12 are assembled, the tulip 22 canpivot about the shaft 16 limited by the projection 114 abutting eitherside of the recessed slot 109.

With reference to FIGS. 10-12, a spinal cord 2 is illustrated havingvertebrae 4 some of which had been previously fused and fixed with apre-existing rod 101 and pedicle screw assembly 200. On each side of thespinous process there is shown a pre-existing pedicle screw and rodassembly 200 with the pre-existing rod 101. The spinal implant revisiondevice 10 of the present invention is shown physically attached to thepre-existing rod 101 at the connector 12 and extending upward along thespine to a second pedicle screw and tulip assembly 300, interposedbetween the second pedicle screw assembly 300 is a rod 102. Thesecomponents will all be new components being added to the spine during asurgical procedure. As such, the revision connector 10 when attached tothe pre-existing rod 101 enables the implant revision device to beinserted through incisions minimally invasively in such a fashion thatthe connector and tulip assembly with tower (not shown in FIGS. 10-12)can be positioned. The connector 12 is attached to the pre-existing rod101 and fixed with the tower leg extension 26, 28 partially extendingoutward of the incision outward and external of the patient's body.Entry of the second rod 102 can be accomplished as taught in U.S. Pat.No. 8,956,361 entitled “Extended Tab Bone Screw System” which isincorporated herein by reference in its entirety.

When such a rod 102 is passed through the channel 24 in the legextensions 26, 28 of the tower, it is noted that the bridge 27 extendingbetween each leg extension 26, 28 can allow a tool to pivot about it. Inthe present invention these bridges 27 are shown at the proximal end ofthe tower 20, however, they can be reduced and slightly submerged toprovide better control of the tool upon assembly. However, it isimportant to have the bridges 27 because they provide rigidity of thetower 20 and insures the leg extensions 26, 28 do not inadvertentlybreak prematurely during a surgical procedure. Ideally, the legextensions 26, 28 are maintained in their position until the rod 102 isfully positioned into the lower portion of the tulip 22 at which timethe set screw 30 can tighten the rod 102 onto the lower saddle portion36 and upper saddle portion 34.

With reference to FIG. 9, it is clearly shown that an angularinclination θ can be achieved relative to first rod 101 such that thisinclination allows the second rod 102 to be inclined directionallytowards the center of the spine. This is important because of the secondrod 102 is positioned laterally outward of the center portion of thespine 2 due to the fact that the connector 12 is attached to the spine 2and the tulip 22 is outward of the connector 12. Accordingly, whenattaching the second rod 102 to the spine 2, it is important that someangularity can be achieved. This angularity can change from − to + asshown in the constructs. The angle, when set, is defined as θ, this θcan be a −θ or a +θ as previously discussed.

With reference to FIG. 11, a top view of the spine 2 is shown. In thisview, the pre-existing implant assembly 200 is shown with a pre-existingrod 101. The connector 12 of the spinal implant revision device 10 isshown connected to this rod 101. The tulip 22 outboard of the connector12 has the rod 102 shown inclined in such a fashion that the rod 102creates the angle θ relative to the first rod 101. In this fashion, thetulip 22 being outboard of the connector 12 allows the rod 102 todirectionally angle inwardly towards the center of the spinal column 2as illustrated. When this occurs, the entire assembly is moredirectionally in line with the pre-existing assembly 200. At thelocation 300, where a new pedicle screw and tulip assembly 300 can beinserted into the pedicle on each side of the spinous process. Thisinsures a fixation occurs between the next adjacent vertebrae 4.

With reference to FIG. 12, the inclination of the rod 101 from thepre-existing assembly 200 is shown wherein the new rod 102 attached to anew pedicle screw assembly 300 and fixed to a pedicle of an adjacentvertebrae 4 can be angled by an angle α. When the tulip 22 is secured bythe set screw 40, this angle α is fixed relative to first rod 101. Suchinclination variations both inwardly and upwardly allow the spine 2 totake a more natural configuration and allow the surgeon to achieve asecure revision attachment that enables the spine to fuse directly abovethe pre-existing assembly 200 without the need to remove any parts.

As shown in FIG. 7A, the revision connector 12 can have the shaft 16perpendicular to the recess slot or groove oriented at an angle β of 0degrees. In this embodiment shown in FIG. 7A, the range of angularityfor θ− to θ+ is limited to about −5 to +5 degrees by the movement of thesaddle portions 34, 36 in the channel 24 for the rod 102 relative to therod 101. In FIG. 7B, the shaft 16 is shown oriented at an angle β cantedabout 10 degrees relative to the revision connector 12. This allows thesame angular range θ− to θ+ of about −5 to +5 degrees in addition to theangle β. In FIG. 7C, the shaft 16 is canted at an angle β of about 20degrees. This shaft 16 orientation can be made with a right hand or aleft hand orientation wherein the shaft orientation for the right is amirror image of the left. Accordingly, the surgeon would preferablyselect both a left and a right hand revision connector for a singleprocedure if the same inclination is required on each side of the spine,see FIG. 11.

It must be appreciated that the angularity between the rod 101 and rod102 can be made to virtually any inclination desired by the amount ofrod 102 movement in the two piece saddle 34, 36 and the shaft 16 angleselected. Similarly the distance between the rods 101, 102 can beincreased or decreased by changing the shaft 16 distance or lengthrelative to the closed end of the slotted opening 15.

Variations in the present invention are possible in light of thedescription of it provided herein. While certain representativeembodiments and details have been shown for the purpose of illustratingthe subject invention, it will be apparent to those skilled in this artthat various changes and modifications can be made therein withoutdeparting from the scope of the subject invention. It is, therefore, tobe understood that changes can be made in the particular embodimentsdescribed, which will be within the full intended scope of the inventionas defined by the following appended claims.

What is claimed is:
 1. A spinal implant revision device comprising: arevision connector for attachment to a pre-existing rod in a patient,the revision connector having a slotted opening configured to receive afirst or a pre-existing rod; and a tulip member pivotally connected tothe revision connector and movable in angularity within predeterminedranges in a first plane, the first plane being parallel to a rod towhich the revision connector is attached, the tulip configured toreceive a second or new rod wherein the tulip member can rotate withinthe first plane in a predetermined angular range α− to α+, wherein theangular range of α− to α+ is between −15 degrees to 15 degrees wherein 0degrees is parallel to a longitudinal axis of the pre-existing rod, therange of angles α− to α+ allows the second or new rod to be tiltedeither upwardly or downwardly relative to the first or pre-existing rodto permit installation at different levels relative to the spine, andwherein the tulip member has a lower rod receiving portion and anelongated detachable tower portion connected integral to the lower rodreceiving portion by a breakaway groove positioned therebetween, thelower rod receiving portion of the tulip is formed as a second or newrod receiving slot or channel extending to a closed end, a pair of legsextend from the closed end defining the second or new rod receiving slotor channel to the breakaway groove, the elongated detachable towerportion has a pair of detachable leg extensions, one leg extensionextending from the breakaway groove and aligned with one of the legsfurther extending the receiving slot or channel toward a proximal endwherein the second or new rod receiving slot or channel extends openthrough and between legs and leg extension to receive the second or newrod therethrough external of a patient and configured to deliver saidrod internal an incision to the closed end of the tulip, and wherein thetulip has a side with a projection interposed between the connector andthe inner surface of the connector, the projection fits into acomplimentary truncated “V” shaped recessed slot configured to limit theangularity of the connector relative to the tulip within thepredetermined range α− to α+ when the tulip and revision connector areassembled the tulip can pivot limited by the projection abutting sidesof the truncated “V” shaped recessed slot.
 2. The spinal implantrevision device of claim 1 wherein a second plane lies transverse to thefirst rod and allows the revision connector and tulip member to bendwithin a predetermined angle range θ to θ+ on assembly relative to thefirst or pre-existing rod and the second or new rod.
 3. The spinalimplant revision device of claim 2 wherein the angular range within thesecond plane is θ− to θ+ between −15 degrees and 15 degrees wherein 0degrees is perpendicular to the first or pre-existing rod, the range ofangles θ− to θ+ allows the new second rod to be angled relative to thefirst or pre-existing rod inward or outward relative to the first orpre-existing rod to permit installation directionally within the secondplane toward or away from a centerline of a spine.
 4. The spinal implantrevision device of claim 1 wherein the leg extensions and the legs haveinternal threads to receive a compression screw for securing the secondor new rod.
 5. The spinal implant revision device of claim 1 wherein ator near the proximal end the leg extensions further comprises a pair ofbridge connections spanning the respective channel connecting each legextension.
 6. The spinal implant revision device of claim 1 wherein thetulip comprises a projection configured to limit the angle of angularmovement α− to α+, the projection extending between the tulip and therevision connector, the revision connector further comprises a recessedslot to receive the projection and sized larger to permit the range ofangularity α− to α+ and θ− to θ+.
 7. The spinal implant revision deviceof claim 1 wherein the revision connector has a shaft extendingoutwardly for coupling to the tulip member, the tulip member having afirst receiving hole for passing a shaft and a second receiving hole forpassing an end of the shaft therethrough.
 8. The spinal implant revisiondevice of claim 7 wherein the revision connector slotted opening forreceiving a first or pre-existing rod extends inwardly toward the tulipmember to a closed end, the revision connector having a threaded openingabove the slotted opening to receive a threaded set screw with a convexor conical or frustoconical shaped tip, and wherein tightening the setscrew directs the tip of the set screw to engage the first orpre-existing rod external surface outward of the rod's longitudinal axisas tightening of the set screw draws the revision connector closed endto move tightly against the first or pre-existing rod securing the firstor pre-existing rod between the closed end and the tip of the set screw.9. The spinal implant revision device of claim 8 wherein the end of theshaft of the revision connector is swedged or flared outwardly topivotally movably fix the revision connector to the tulip member withinthe angular range α− to α+ fixed to the projection and the truncatedrecessed slot.
 10. The spinal implant revision device of claim 7 whereinthe shaft has a concavity or depression on an upper surface to receive asaddle assembly and the implant device further comprises a two piecesaddle, a first lower saddle portion with a bottom “U” shaped openingoriented to fit over the shaft and an upper saddle portion with an upper“U” shaped opening for receiving the second or new rod and wherein theupper saddle portion is movable relative to the lower saddle portion sothe second or new rod can be moved within the range of angles θ− to θ+.11. The spinal implant revision device of claim 10 wherein the uppersaddle portion has a convex bottom that passes through the lower saddleportion to the depression on the shaft when a set screw tightens therod.